Life cycle and vector

Malaria is a protozoal infection transmitted to human beings by female mosquitoes. In total there are nearly 120 species of Plasmodia, including at least 22 found in primate hosts, and 19 in rodents, bats and other mammals. About 70 other Plasmodia species have been described in birds and reptiles. Human malaria is caused by five species of Plasmodium, namely P. falciparum, P. vivax, P. ovalae, P. malariae and P. knowlesi. These five species of human malaria parasites differ morphologically, immunologically, in geographical distribution, relapse pattern and drug response. Of the five human malaria parasites, Plasmodium falciparum is the most virulent and causes the most fatalities.

Figure 1.1: The life cycle of the human malaria parasite, Plasmodium spp.

The malarial life cycle is split between a vertebrate host and an insect vector. These five Plasmodium species, with the exception of P. malariae and P. knowlesi (which also affects higher primates) are parasites exclusive to man.

The mosquito is always the vector, and is always an Anopheline mosquito, although, out of the 380 species of Anopheline mosquito, only 60 can transmit malaria, some 30 of which are of major importance. Only female mosquitoes are involved, as the males do not feed on blood.